Researchers Moffitt Cancer Center have reported encouraging early results from a clinical trial testing whether immunotherapy can improve treatment for men with one of the most dangerous forms of prostate cancer.
The findings were published in the Journal for ImmunoTherapy of Cancer.
Prostate cancer is one of the most common cancers in men. Many cases grow slowly and can often be treated successfully.
However, some forms are much more aggressive and difficult to control. One of the most dangerous types is known as Grade Group 5 prostate cancer.
Grade Group 5 tumors grow quickly and are more likely to spread outside the prostate to other parts of the body. Because of this, patients with this diagnosis face a much higher risk of life-threatening disease.
Doctors already use several powerful treatments for these high-risk patients, including hormone therapy and radiation therapy. Hormone therapy works by lowering or blocking male hormones that help prostate cancer grow. Radiation therapy uses high-energy rays to damage and kill cancer cells.
Even with these treatments, aggressive prostate cancer can still return after therapy. Researchers therefore continue searching for ways to improve long-term outcomes.
The new study explored whether adding immunotherapy could help.
Immunotherapy is a type of cancer treatment that helps the body’s immune system recognize and attack cancer cells more effectively. In this study, researchers used a drug called Nivolumab.
Nivolumab belongs to a class of medicines called checkpoint inhibitors. Normally, cancer cells can hide from the immune system by using certain “checkpoint” signals that prevent immune cells from attacking them. Nivolumab blocks one of these signals, allowing immune cells to better recognize and fight cancer.
The researchers believed that combining nivolumab with radiation therapy might create a stronger immune response against prostate cancer.
Radiation therapy can break apart cancer cells, releasing pieces of the tumor that may alert the immune system. Scientists hoped nivolumab would help immune cells react more strongly to those signals and destroy any remaining cancer cells more effectively.
The phase 2 clinical trial included 31 men with highly aggressive Grade Group 5 prostate cancer.
All participants received intensive treatment involving several therapies together. Patients first underwent hormone therapy along with two types of radiation treatment.
One form of radiation, called high-dose-rate brachytherapy, delivers radiation directly inside the prostate using small radioactive sources placed near the tumor. The second form, called external beam radiation therapy, delivers radiation from outside the body.
Patients also received nivolumab beginning about one month before radiation treatment started. The drug was then continued during therapy.
The results were encouraging.
After two years, about 90% of the patients showed no biochemical evidence that their cancer had returned. Researchers monitored this using PSA blood tests, which measure levels of prostate-specific antigen, a protein that can rise when prostate cancer becomes active again.
The researchers noted that these results appear better than outcomes previously reported for similar high-risk patients treated with standard therapy alone.
Importantly, the combination treatment was also generally well tolerated. Researchers reported no severe toxic side effects, which is especially important because the treatment approach was very intensive.
The study also uncovered another potentially important finding.
Researchers observed that patients with higher Decipher immunosuppression scores appeared to respond better to treatment. This score is a genomic test that examines how the immune system interacts with a tumor and whether the cancer may be suppressing immune activity.
Scientists believe this type of biomarker may eventually help doctors predict which patients are most likely to benefit from immunotherapy.
Senior author Kosj Yamoah, chair of Radiation Oncology at Moffitt Cancer Center, explained that the goal was to activate the immune system earlier in treatment so it could better respond once radiation began destroying cancer cells.
He said one of the most encouraging findings was the low rate of cancer recurrence after two years in such a high-risk patient group.
Still, researchers caution that the study remains early-stage and has important limitations.
The trial was a single-arm study, meaning all patients received the same treatment and there was no separate comparison group receiving standard treatment alone. Because of this, scientists cannot yet prove that nivolumab was directly responsible for the improved outcomes.
Larger randomized clinical trials will be needed to confirm whether the immunotherapy combination truly improves survival or reduces recurrence compared with current standard care.
Researchers also need longer follow-up because prostate cancer can sometimes return many years after treatment.
Even so, experts say the findings are promising because aggressive Grade Group 5 prostate cancer remains extremely difficult to treat successfully over the long term.
The study reflects growing interest in combining radiation therapy with immunotherapy in cancer treatment. Scientists believe radiation may help “wake up” the immune system, while checkpoint inhibitors such as nivolumab may strengthen the body’s ability to attack cancer cells.
If future studies confirm these results, doctors may eventually be able to personalize treatment using biomarkers like the Decipher score to identify patients most likely to benefit from immunotherapy.
The findings provide hope that combining multiple advanced therapies may improve outcomes for patients facing one of the most dangerous forms of prostate cancer.
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